1. Field of the Invention
The present invention relates to control apparatus and method for vehicle equipped power supply and particularly relates to a technique to diagnose a deterioration of a vehicular battery with a high accuracy although an inexpensive structure.
2. Description of the Related Art
In general, a battery is mounted in a vehicle as a power supply for a starter to perform a cranking and other electrical parts. The battery is chargeable or dischargeable and it is usual practice that an output voltage level (a charged state of the battery) is controlled to a predetermined level by controlling a generated power of an alternator in accordance with an actual charged state of the battery and in accordance with a driving state of an engine. In addition, in a hybrid vehicle in which an electric motor is disposed as a drive source except the engine, this electric motor is used as the starter to enable the cranking. A Japanese Patent Application First Publication No. 2001-268708 published on Sep. 28, 2001 (which corresponds to a U.S. Pat. No. 6,659,213 issued on Dec. 9, 2003) exemplifies a previously proposed diagnostic apparatus for diagnosing the deterioration of the vehicle mounted battery. With a connection between the battery and the electrical load therefore interrupted, a terminal voltage of the battery is detected as an electromotive force E0, during the large current discharge state along with the cranking the terminal voltage across the battery is detected as V0 and a discharge current thereat is detected as I. On the basis of the detected, E0, V, and I, an internal resistance R of battery is calculated in accordance with the following equation (1), and a magnitude of the calculated R is deemed to be the degree of deterioration of the battery.R=(E0−V)/I  (1).